Alkali soluble and alkali swellable emulsion polymers and copolymers are well known (see e.g. Pat. Nos. 3,003,987; 3,070,561, and 3,081,198) and are useful in coatings, textile sizings, textile printing pastes, paints and industrial coatings where a water soluble resin can be utilized. They are also useful as thickening agents in latex based adhesives, where clays, other fillers, pigments and the like are present. In addition, alkali soluble emulsion polymers and copolymers find application in cleaners, laundry detergents, lotions and other personal care products. In petroleum exploration, acrylic polymers are used as drilling fluid additives for viscosity control and as bentonite extenders for enhancing performance of the drilling fluid. Thus, according to U.S. Pat. No. 4,301,016 water soluble alkali metal polyacrylates are useful additives in drilling fluids based on fresh water.
In drilling muds acrylics have performed well in fresh water drilling, U.S. Pat. No. 4,301,016, supra, and U.S. Pat. No. 2,718,497, but acrylics have poor salt tolerance as compared to some cellulosic materials. On the other hand acrylics and other synthetic polymers and copolymers offer a major advantage in manufacturing reproducability, as compared to chemically grafted or modified natural products, provided the salt tolerance problem is not a factor.
The resistance of acrylic polymers to biological decay is a property which is especially beneficial in drilling muds, paints, cleaner solutions, and personal care products. In order to provide improved properties for specific applications, functional polymeric side chains have been added to synthetic acrylic systems.
In various industrial applications, acrylics available as liquid emulsions and dispersions are generally easier to use than modified natural polymers which usually are dry powders, since the former are capable of addition at most any point in a mixing process. On the other hand, dry products based on starches, cellulose, and proteins require a relatively long hydration time and take longer to dissolve than the soluble alkali metal polymers.
U.S. Pat. No. 3,657,175 discloses improved thickening agents based on acrylics, styrene and butadiene, containing bound surfactant groups.
As shown by U.S. Pat. Nos. 4,384,096; 4,351,754, and 4,421,903, improved thickeners for aqueous systems have been developed in which there are introduced to the acrylic polymer backbones ester surfactant groups in sufficient number to enhance thickening and rheological properties. These thickeners find use in paints, coatings, adhesives, cleaners, drilling fluids, textile printing inks, personal care products, and the like.